> From: Kristoff > Date: Thu, 14 Nov 2019 23:39:32 +0100
[snip] > Question: > > I am trying to find a way to use the 19 KHz stereo-pilot signal to > create a 57 KHz carrier (to down-convert the FM/RDS carrier at 57 > KHz). > > How do I do this? Use the PLL carrier tracking block which will simultaneously: 1) phase lock to the 19 kHz pilot tone 2) shift (in reality rotate) the spectrum of the signal so the 19 kHz tone gets moved to 0 Hz. After that use a Rotator block to shift the spectrum another 38 kHz = 57 kHz - 19 kHz Then use an FIR/FFT filter block with low pass taps to isolate your RDS signal. > > Itried using a PLL carrier-tracking block to extract the 19 KHz > carrier (which seams to work) and direct that carrier to a 3 input > multiplier block, but that does not seams to work. Even after > filtering out DC and the carrier at -19 KHz (negative frequency), > the output of the multiplier is always zero. (*) You have neglected that that PLL block performs a spectrum shift as well as tracking the pilot signal. Put a QT GUI Freq sink on the output of the PLL carrier tracking block to see. > > Or is there a better way to generate a 57 KHz complex sine-wave from > a 19 KHz reference signal? There is no need to have a locally generated 57 kHz carrier, when you can just use a PLL to phase lock and then a rotator to shift the spectrum. -Andy
